Rationale: Combined positron emission tomography-computed tomography (PET-CT) has emerged as a tool for detecting and delineating lesions, staging and restaging disease, and predicting and monitoring response to treatment. The rationale for this imaging strategy is that accuracy may be improved by combining 2 types of data.

Technology Description: PET-CT is an imaging technique that merges physiologic data from positron emission tomography (PET) and morphologic data from computed tomography (CT). The goal of PET-CT as a diagnostic tool for patients with neuroendocrine tumors (NETs) with an unknown primary site is to provide optimal imaging capability by minimizing misalignment between PET and CT images in order to identify and localize primary tumors.

Controversy: PET-CT offers an alternative to other conventional diagnostic modalities for the identification and localization of unknown primary tumors in patients with metastatic NETs. However, a definitive reference standard other than histopathology for detection of unknown primary tumors is lacking, which makes evaluation of PET-CT for this indication challenging.

Key Questions

  • Can PET-CT accurately localize the primary tumor in patients with NETs of unknown origin?
  • Does use of PET-CT in patients with NETs with primary tumors of unknown origin change patient management or improve outcomes? 
  • Is PET-CT in patients with NETs of unknown origin safe?
  • Have definitive patient selection criteria for the use of PET-CT for identifying primary tumor in patients with NETs of unknown origin been established?

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